Where exactly do asbestos come from?

It is mined: Asbestos is a naturally occurring mineral that is mined, much like gold, copper and coal. It is composed largely of silicon and has been used for everything from insulation to fire-proofing. When the fibers are inhaled, they can cause significant lung damage and disease. It has been largely banned from building materials in the us. http://en.wikipedia.org/wiki/asbestos.

Depends on country: Asbestos includes 6 different mineral types, gained by mining for it. It was primarily used in house and building construction until laws regulating asbestos usage developed in the late 1900's, in the USA. Different countries have different, or no, regulations on its use. See this article for an international summary: On behalf of Nevada’s DHCFP